Gas filled envelope for a spark gap or the like



April 9, 1968' F. FRUENGEL ETAL 3,377,496 GAS FILLED ENVELOPE FOR A SPARK GAP OR THE LIKE Filed July 6, 1966 United States Patent Claims The present invention relates to a gas filled envelope for spark gaps, high pressure flash lamps and the like.

Gas filled envelopes or glass bulbs in which a spark discharge at high energy takes place are used up in a relatively short time since the glass bulb becomes blackened at the inside and cannot be cleaned without detrimentally affecting the gas filling. It is therefore customary to discard such gas filled envelopes including the electrode system incorporated therein after the glass bulb has blackened.

It is an object of the present invention to provide for an improved gas filled envelope of the aforementioned type which can be regenerated by the user with a minimum expenditure of apparatus and labor, so that the relatively large cost of replacing the gas'filled envelope and associated elements may be saved and any time loss which may occur by ordering the gas filled envelope from a distant supplier may be avoided.

It is an additional object of the present invention to provide for a gas filled envelope of the aforementioned type in which the gas filling may be easily replaced, when such replacement is necessary after cleaning of the interior of the envelope.

With these and other objects in view, the gas filled envelope according to the present invention for spark gaps and the like mainly comprises a filling tube gas-tightly connected to the envelope and communicating at one end thereof with the interior of the envelope. The tube has a portion projecting outwardly of the envelope and an outer free end and closure means are arranged at the free end of the filling tube movable between a first position gas tightly closing the free end of the tube and a second position permitting passage of gas through the tube..Fitting means are removably and gas tightly fitted over the aforementioned outwardly projecting portion of the filling tube, the fitting means defining an enclosed spacewhich communicates with the interior of the tube when the closure means is in the open position, and operating means having an engaging portion in the enclosed space of the fitting means and adapted to be brought into engagement with the closure means and an operating portion extending gas tightly sealed from the aforementioned space to the outside of the fitting means are arranged so as to be operable for moving said engaging means into engagement with the closure means and to move the latter between the positions thereof. Furthermore passage means are provided which communicate at one end thereof with the enclosed space and which are adapted to be connected at the other end thereof to apparatus for causing flow of gas through the passage means into and out of the space, and at least one shut-off valve is arranged in the aforementioned passage means for opening and closing the latter.

The closure means is preferably in the form of a screw plug which can be threaded into and out of an inner screw thread provided in the outer end of the filling tube and in this case the operating means is preferably in the form of a screwdriver coaxially arranged with the screw plug.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing, in which:

The only figure is a schematic, partly sectioned view of the apparatus according to the present invention.

Referring now to the drawing, it will be seen that the apparatus according to the present invention mainly comprises a gas filled envelope 1 which may for instance be in the form of a spherical bulb formed for instance from quartz glass which is provided with a pair of axially aligned and oppositely arranged spaced electrodes 2 and 3 which extend gas tightly sealed through opposite tubular extensions 5 of the bulb 1. A pair of sleeves 4 are arranged about the tubular extensions 5 and connected with inner portions thereof to outer flanges of the tubular extensions 5 in any convenient manner, whereas outer portions of the sleeves 4 are provided with an inner screw thread into which centrally bored plugs 6, provided with an outer screw thread, are respectively threadedly engaged so as to press O-rings 7 of resilient material against the end faces of the tubular extension 5 and against the outer cylindrical surface portions of the electrodes 2 and 3, respectively. When the screw plugs 6 are tightened and the O-rings 7 compressed, a gas tight seal is provided preventing escape of gas under pressure from the interior of the envelope 1 to the outside thereof.

One of the electrodes, for instance the electrode 3, is provided with an axial bore 8 ending short of the inner end of the electrode and a transverse bore 9 communicates with the inner end of the axial bore 8 to thus provide communication between the axial bore 8 and the interior of the envelope 1. The electrode 3 thus provided with the bores 8 and 9 constitutes therefore a filling tube through which gas may be filled into the interior of the envelope 1 and be evacuated therefrom. The outer, or left end, as viewed in the drawing, of the electrode 3 is provided with a bore portion having a larger diameter than the remainder of the bore so as to form at the junction of the large diameter portion and the remainder of the bore a shoulder, and the large diameter portion of the bore is provided with an inner screw thread 13 into which a screw plug 10 is screwed provided at its outer, or left end with a screw slot 11. The opposite end of the screw, plug is provided with a small diameter projection 12 which fits into the axial bore of the electrode 3 and around which an annular gasket 13 is located so that the gasket 13 is pressed against the aforementioned shoulder when the screw plug 10 is tightly screwed into the threaded bore end portion of the electrode 3. The screw plug 10 forms therefore closure means movable between a first position for closing the passage through the electrode or filling tube 3 and a second position, that is screwed out of the threaded end of the electrode 3, for permitting passage of gas through the electrode.

The arrangement includes further fitting means 14 in form of a preferably cylindrical member formed with an axial bore 15 extending from one end in the cylindrical member and having an inner diameter substantially equal to the outer diameter of the electrode 3 so that the outer end of the electrode 3 may be pushed into the cylindrical bore 15 of the filling means 14. The right end, as viewed in the drawing, of the cylindrical member 14 is provided with an enlarged bore portion formed with an inner screw thread into which an axially bored screw plug 16 is threadingly engaged so that an O-ring 17 located between the inner end of the screw plug 16 and the corresponding shoulder in the member 14 may be compressed and so that the inner surface of the O-ring 17 is pressed tightly against the outer surface of the electrode 3 located in the bore 15 to provide a fluid tight seal 3 between the bore and the outer surface of the electrode 3. The bore 15 defines therefore in the member 14 an inner space which is gas tightly sealed from the outer atmosphere.

The arrangement includes also operating means in the form of a screwdriver 18 having an engaging portion 18' in form of a screwdriver blade in the enclosed space defined by the bore 15 and an operating portion extending gas tightly sealed from the space to the outside of the fitting means and provided at the outer end with a handle portion, which may be spherical. The stem of the screwdriver which connects the handle portion 21 with the screwdriver blade 18 extendsthrough a central bore of a screw plug 19 screwed into a correspondingly threaded enlarged bore portion formed in the left end, as viewed in the drawing, of the member 14 and an O-ring 20 located about the stem and between the inner end of the screw plug 14 and a corresponding shoulder on the member 14 serves, when compressed, to provide a fluid tight seal about the stem of the screwdriver 18. This seal provided by the O-ring 20 is compressed in such a manner so as to permit axial movement of the operating means or screwdriver 18 and turning of the latter about its axis.

At least one, but as shown in the drawing, preferably two passage means 22 and 23 are provided which communicate with the inner end thereof with the bore 15 to the left, as viewed in the drawing, of the screw plug 10 and shut-off valves 24 and 25 of known construction cooperate respectively with the passage means 22 and 23 for opening and closing the latter. The valves 24 and 25 are respectively connected to a source of gas under pressure and to a vacuum pump, not shown in the drawing.

The above described arrangement will operate as follows:

During normal operation of the spark gap constituted by the envelope 1 and the electrodes 2 and 3, the fitting means 14 and the elements associated therewith are removed from the electrode 3 and the plug 10 is tightly screwed into the left end, as viewed in the drawing, of the electrode 3 so as to gas tightly close the passage 8 formed therethrough. The electrodes 2 and 3 are then connected in known manner to a source of electrical energy. If after extended use of this arrangement the interior of the gas bulb becomes blackened, the electrodes 2 and 3 are disconnected from the source of electrical energy, the screw plugs 6 are unscrewed from the sleeves 4 so that the electrodes may be removed and the interior of the glass bulb 1 may be cleaned through the thus formed openings. Afterwards, the electrodes 2 and r 3 are inserted again, the screw plugs 6 are tightened so that the electrodes are again gas tightly connected to the glass bulb 1. The fitting means 14 is then placed over the left. end, as viewed in the drawing, of the electrode 3, the screw plug 16 is tightened sothat the fitting means are gas tightly connected to the outer end of the electrode 3. The operating means or the screwdriver 18 are then operated, that is moved inwardly so that the screwdriver blade 18' engages in the screw slot 11 of the plug 10 and then the screwdriver is turned to unscrew the plug 10 from the thread provided in the outer end of the electr'ode, whereby the plug 10 is withdrawn into the bore 15. After the passage 8, 9 through the electrode 3 has thus been opened, one of the valves 24 or 25, that is the valve which is connected to the vacuum pump is opened so that theinterior of the envelope may be evacuated, and after the evacuation is completed the valve in the line between the vacuum pump and the bore1'5 is closed and the other valve connected to a source of gas under pressure is opened so that such gas will enter into the Y bore 15 and pass through the passage 8,9 in the electrode 3 into the interior of the evacuated envelope 1. The gas used for filling the interior of the envelope 1 is preferably a rare or inert gas, for instance krypton with an addition of helium. The pressure at which the envelope is filled with gas will depend and is adjusted according to the desired st'z'e of the spark to be formed between the spaced ends of the electrodes. After the filling of the envelope with gas under pressure is finished the other valve is also closed and the screw plug 10 is again screwed into the threaded end portion of the electrode 3 by means of the screwdriver 18 to provide a gas tight seal at the outer end of the electrode 3. Subsequently thereto, the fitting means 14 is removed from the outer end of the electrode 3.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of gas filled envelope differing from the types described above.

While the invention has been illustrated and described as embodied in a gas filled envelope with means for replacing the gas filling of the envelope, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

For instance while in the illustrated arrangement the electrode '3 provided with the bores 8 and 9 is used as a filling tube, it is evidently also possible to omit the bores 8 and 9 from the electrode 3 and to provide a separate filling tube which communicates at the inner end thereof in a gas tight manner with the envelope 1. In this case the outer end of the filling tube is provided with a closure means as described above and the fitting means 14 is placed onto the outer end of this separate filling tube. If the envelope is mounted in a space which is not easily accessible, the separate filling tube may be of considerable length and at least a portion thereof may be in the form of a flexible hose.

It is also possible to provide only a single passage means communicating with the space 15 and a single valve located in the passage means and connected to a source of gas of pressure. In this case the other electrode is preferably also formed with a closable bore so that instead of first evacuating the interior of the electrode, a rare gas under pressure may be fed from a source of gas under pressure through the open shut-off valve and through the bored electrode 3 into the interior of the envelope 1 to displace any air therein which passes out through the bore in the other electrode until the interior of the envelope is completely filled with rare gas after which the bores in both electrodes are closed again.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a gas filled envelope for a spark gap and the like, in combination, a filling tube gas tightly connected to said envelope and communicating at one end thereof with the interior of said envelope, said tube having a portion projecting outwardly of said envelope and having a free end; closure means at said free end of said filling tube, said closure means being movable between a first position gas tightly closing said free'end of said tube and a second position permitting passage of gas through said tube; fitting means removably and gas tightly fitted over said portion of said filling tube, said fitting means defining an enclosed space communicating with the interior of said tube when said closure means is in said open position; operating means having an engaging portion in said enclosed space adapted to be brought into engagement with said closure means, and an operating portion extending. gas tightly sealed from said space to theoutside of said fitting means so as to be operable for moving said engaging means into engagement with said' closure means and to move the latter between said position thereof; passage means communicating at one end thereof with said enclosed space and adapted to be connected at the other end thereof to apparatus for causing flow of gas through said passage means into and out of said space; and at least one shut-off valve in said passage means for opening and closing the latter.

2. In a gas filled envelope as set forth in claim 1, wherein said envelope is provided with a tubular extension and including means for removably and gas tightly connecting said one end of said filling tube to said tubular extension.

3. In a gas filled envelope as set forth in claim 1, said closure means comprising a plug located in said first position at least partly in said free end of said tube and being in said second position withdrawn into said enclosed space.

4. In a gas filled envelope as set forth in claim 3, wherein said operating means is aligned along a common axis with said plug.

5. In a gas filled envelope as set forth in claim 1, wherein said free end of the tube is provided with an internally threaded portion, and said closure means comprising a screw plug which in said first position is screwed into said internally threaded portion and in said second position unscrewed therefrom and Withdrawn into said space. Y

6. In a gas filled envelope as set forth in claim 5, wherein said filling tube has at said free end thereof a portion having a larger inner diameter than the remainder of said tube so as to form a shoulder at the junction of said portion and the remainder of said tube, said portion of larger inner diameter being internally threaded, and including a gasket at the end of said screw plug facing said shoulder, said gasket engaging said shoulder when said screw plug is in said first position.

7. In a gas filled envelope as set forth in claim 5, wherein said screw plug has at the outer end thereof facing said engaging portion of said operating means a screw slot, and wherein said operating means is aligned along a common axis with said screw plug, said engaging portion of said operating means being in the form of a screwdriver blade, said operating means being mounted in said fitting means movably in direction of, and turnably about, said common axis.

8. In a gas filled envelope as set forth in claim 7, wherein said enclosed space in said fitting means is at least partly defined by a cylindrical surface aligned along said common axis and having a diameter only slightly larger than that of said screw plug to substantially prevent the latter from tilting when said screw plug is unscrewed from said end of said filling tube and withdrawn into said enclosed space.

9. In a gas filled envelope as set forth in claim 1, wherein said passage means includes two separate passages, and a shut-off valve in each of said passages.

10. In a gas filled envelope as set forth in claim 1, wherein said filling tube is in the form of an electrode formed with an axial bore communicating at the inner end of said electrode with the interior of said envelope.

11. In a gas filled envelope as set forth in claim 1 and including a pair of electrodes extending gas tightly sealed into said envelope, one of said electrodes being formed with an axial bore communicating at the inner end thereof with the interior of said envelope, said one electrode constituting said filling tube.

12. In a gas filled envelope as set forth in claim 11, wherein said electrodes are gas tightly and removably connected to said envelope.

References Cited UNITED STATES PATENTS 1,616,214 2/1927 Brown 313 2,703,374 3/1955 Fruengel 313184 X 3,256,383 6/1966 Sasoror 17417.07

JAMES W. LAWRENCE, Primary Examiner. R. L. JUDD, Assistant Examiner. 

1. IN A GAS FILLED ENVELOPE FOR A SPARK GAP AND THE LIKE, IN COMBINATION, A FILLING TUBE GAS TIGHTLY CONNECTED TO SAID ENVELOPE AND COMMUNICATING AT ONE END THEREOF WITH THE INTERIOR OF SAID ENVELOPE, SAID TUBE HAVING A PORTION PROJECTING OUTWARDLY OF SAID ENVELOPE AND HAVING A FREE END; CLOSURE MEANS AT SAID FREE END OF SAID FILLING TUBE, SAID CLOSURE MEANS BEING MOVABLE BETWEEN A FIRST POSITION GAS TIGHTLY CLOSING SAID FREE END OF SAID TUBE AND A SECOND POSITION PERMITTING PASSAGE OF GAS THROUGH SAID TUBE; FITTING MEANS REMOVABLY AND GAS TIGHTLY FITTED OVER SAID PORTION OF SAID FILLING TUBE, SAID FITTING MEANS DEFINING AN ENCLOSED SPACE COMMUNICATING WITH THE INTERIOR OF SAID TUBE WHEN SAID CLOSURE MEANS IS IN SAID OPEN POSITION; OPERATING MEANS HAVING AN ENGAGING PORTION IN SAID ENCLOSED SPACE ADAPTED TO BE BROUGHT INTO ENGAGEMENT WITH SAID CLOSURE MEANS, AND AN OPERATING PORTION EXTENDING GAS TIGHTLY SEALED FROM SAID SPACE TO THE OUTSIDE OF SAID FITTING MEANS SO AS TO BE OPERABLE FOR MOVING SAID ENGAGING MEANS INTO ENGAGEMENT WITH SAID CLOSURE MEANS AND TO MOVE THE LATTER BETWEEN SAID POSITION THEREOF; PASSAGE MEANS COMMUNICATING AT ONE END THEREOF WITH SAID ENCLOSED SPACE AND ADAPTED TO BE CONNECTED AT THE OTHER END THEREOF TO APPARATUS FOR CAUSING FLOW OF GAS THROUGH SAID PASSAGE MEANS INTO AND OUT OF SAID SPACE; AND AT LEAST ONE SHUT-OFF VALVE IN SAID PASSAGE MEANS FOR OPENING AND CLOSING THE LATTER. 